Output drivers are used to control a voltage at an output terminal. For example, transistors are used which couple the output terminal to a ground potential terminal and which are controlled by a respective driver control circuit. Based on the control, preferably either a high potential or a low potential is present at the output terminal.
Problems can arise when negative voltages are present at the output terminal. For example, in a CMOS process, when an analogue output driver with an NMOS transistor is used, a parasitic diode between drain and substrate of the transistor becomes forward biased if the output voltage falls below −0.3 Volt with respect to the ground potential. However, if a voltage output low level smaller than 1 Volt is required, an NMOS transistor is preferably used because of the low voltage drop in its conducting state. Therefore, to withstand negative voltages at the output terminal, a diode can be connected between the output terminal and the NMOS transistor. However, the voltage drop across the diode increases the voltage output low level.